044
WTPZ43 KNHC 260848
TCDEP3
TROPICAL STORM SONIA DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP182025
200 AM PDT SUN OCT 26 2025
AFTER EXPERIENCING A LATE AFTERNOON DIURNAL MINIMUM IN CONVECTION ON
SATURDAY DURING WHICH THE STRUCTURE OF SONIA WAS RATHER DISORGANIZED
AND THE INTENSIFICATION OF THE TROPICAL STORM HALTED, DEEP
CONVECTION HAS RETURNED OVER THE CENTER OVERNIGHT, WITH A LARGE AREA
OF CLOUD TOPS COLDER THAN -70C. LIGHT TO MODERATE SOUTHERLY SHEAR
APPEARS TO BE AFFECTING THE STORM JUST A BIT, WITH THE LOW-LEVEL
CENTER SITUATED IN THE SOUTHERN HALF OF THE CONVECTIVE AREA. THE
LATEST SUBJECTIVE INTENSITY ESTIMATES ARE T3.0/45 KT FROM TAFB AND
T3.5/55 KT FROM SAB. THE OBJECTIVE UW-CIMSS NUMBERS HAVE BEEN
RUNNING IN THE 40-45 KT RANGE, AND THE HIGHEST ASCAT VECTOR ON A
RECENT ASCAT PASS WAS 41 KT. THE INITIAL INTENSITY IS HELD AT 45 KT
BASED ON THE ABOVE DATA.
SONIA IS EXPERIENCING ABOUT 10-15 KT OF SOUTHERLY VERTICAL WIND
SHEAR WHILE OVER SEA-SURFACE TEMPERATURES (SSTS) OF ABOUT 27C. THE
SHEAR AND SSTS SHOULD REMAIN ABOUT THE SAME FOR THE NEXT 12-24 H,
BUT SOUTHERLY SHEAR IS FORECAST TO INCREASE FURTHER AFTER THAT TIME
WHILE SSTS BEGIN TO GRADUALLY DECREASE. BY 60 HOURS, SHEAR SHOULD
BE STRONGER THAN 20 KT WHILE SSTS FALL BELOW 26C. MELISSA WILL ALSO
REACH A DRIER AIRMASS AFTER 60 H. THE NHC FORECAST WILL SHOW SLIGHT
STRENGTHENING OVER THE NEXT 24 H WHILE SONIA REMAINS OVER LUKEWARM
SSTS AND MODERATE SHEAR. THEREAFTER, GRADUAL WEAKENING IS EXPECTED,
AND MELISSA SHOULD LOSE ITS CONVECTION AND BECOME A REMNANT LOW BY
DAY 3. THE INTENSITY FORECAST IS AT THE HIGH END OF THE GUIDANCE
SUITE THROUGH THE FIRST 36 HOURS OF THE FORECAST, BUT SHOWS A
SLIGHTLY LOWER PEAK INTENSITY COMPARED TO THE PREVIOUS NHC FORECAST.
THE GFS AND ECMWF SIMULATED SATELLITE PRODUCTS SHOW THE CYCLONE
LOSING ITS CONVECTION BETWEEN 60-72 H, SO THE NHC FORECAST WILL CALL
FOR SONIA TO BECOME A REMNANT LOW BY HOUR 72, AND GRADUALLY
DISSIPATE THEREAFTER.
SONIA HAS BEEN MOVING SLIGHTLY SOUTH OF DUE WEST (265 DEGREES) AT A
SLOW FORWARD SPEED OF 4 KT. A WEAKNESS IN A NARROW SUBTROPICAL
RIDGE TO THE NORTH SHOULD CAUSE SONIA TO TURN TOWARD THE
WEST-NORTHWEST LATER TODAY, BUT STILL AT A VERY SLOW FORWARD SPEED,
BECAUSE THE STEERING CURRENTS OVERALL ARE WEAK. BY TUESDAY, AS THE
CYCLONE WEAKENS, A TURN BACK TOWARD THE WEST WITH AN INCREASE IN
FORWARD SPEED IS EXPECTED AS SONIA IS STEERED PRIMARILY BY THE LOW-
LEVEL FLOW. THE LATEST NHC FORECAST IS A TAD SLOWER THAN THE
PREVIOUS PREDICTION AND LIES GENERALLY BETWEEN THE LATEST HFIP
CORRECTED CONSENSUS APPROACH (HCCA) AND GOOGLE DEEP MIND ENSEMBLE
MEAN (GDMI).
FORECAST POSITIONS AND MAX WINDS
INIT 26/0900Z 13.4N 119.5W 45 KT 50 MPH
12H 26/1800Z 13.5N 119.9W 50 KT 60 MPH
24H 27/0600Z 13.9N 120.6W 55 KT 65 MPH
36H 27/1800Z 14.3N 121.6W 55 KT 65 MPH
48H 28/0600Z 14.7N 122.8W 45 KT 50 MPH
60H 28/1800Z 14.8N 124.3W 35 KT 40 MPH
72H 29/0600Z 14.9N 126.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 30/0600Z 14.5N 129.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 31/0600Z...DISSIPATED
FORECASTER HAGEN
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